ceph-detect-init man page

ceph-detect-init is a utility that prints the init system Ceph uses. It can be one of sysvinit, upstart or systemd. The init system Ceph uses may not be the default init system of the host operating system. For instance on Debian Jessie, Ceph may use sysvinit although systemd is the default.

If the init system of the host operating system is unknown, return on error, unless --default is specified.